GMAT Math : Powers & Roots of Numbers

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #5 : How To Factor A Common Factor Out Of Squares

Which of the following is equal to the following expression?

Possible Answers:

Correct answer:

Explanation:

First, break down the components of the square root:

Combine like terms. Remember, when multiplying exponents, add them together:

Factor out the common factor of :

Factor the :

Combine the factored  with the :

Now, you can pull  out from underneath the square root sign as :

Example Question #6 : How To Factor A Common Factor Out Of Squares

Which of the following expressions is equal to the following expression?

Possible Answers:

Correct answer:

Explanation:

First, break down the component parts of the square root:

Combine like terms in a way that will let you pull some of them out from underneath the square root symbol:

Pull out the terms with even exponents and simplify:

Example Question #31 : Understanding Powers And Roots

Which of the following is equal to the twelfth power of the cube root of ?

Assume  to be positive.

Possible Answers:

Correct answer:

Explanation:

The cube root of  is  raised to the power of one third, or . This raised to the power of twelve is

Example Question #32 : Understanding Powers And Roots

Which of the following expressions is equal to  ?

Possible Answers:

Correct answer:

Explanation:

Example Question #31 : Powers & Roots Of Numbers

Assume  to be positive.

Multiply the eighth power of the fourth root of  by the fourth power of the eighth root of . What is the product?

Possible Answers:

Correct answer:

Explanation:

The fourth root of  is ; the eighth power of this is .

The eighth root of  is ; the fourth power of this is .

The product of these expressions is .

Example Question #34 : Understanding Powers And Roots

Which of the following is equal to the eighth root of the square of ?

Assume  to be positive.

Possible Answers:

The sixteenth power of .

The fourth power of .

The fourth root of 

The sixth root of 

The sixteenth root of .

Correct answer:

The fourth root of 

Explanation:

The square of  is .  The eighth root of  is  raised to the power of , or 

This is equivalent to , the fourth root of .

Example Question #35 : Understanding Powers And Roots

Which of the following numbers has a rational square root and a rational cube root?

Possible Answers:

Correct answer:

Explanation:

Each of the choices is a power of 10, so rewrite each choice as such:

Since 10 itself does not have a rational square root, a necessary and sufficient condition for  to have a rational square root - that is, for

 

to be rational - is for  to be an integer. This allows us to eliminate  and 

Similarly, for  to have a rational cube root,  must be an integer. This allows us to eliminate  and .

 is left.  is the correct choice.

Example Question #36 : Understanding Powers And Roots

Assume  to be negative.

Add the tenth power of the fifth root of  to the fifth root of the tenth power of . What is the expression?

Possible Answers:

Correct answer:

Explanation:

The tenth power of the fifth root of  can be found as follows:

The fifth root of  is ; the tenth power of this is .

The tenth power of  is ; the fifth root of this is 

The two expressions are equivalent, so they add up to .

Example Question #37 : Understanding Powers And Roots

Which of the following is equivalent to ?

Possible Answers:

Correct answer:

Explanation:

This question requires that you understand negative exponents and fractional exponents. To make a negative exponent positive, simply switch its location in the fraction, so this:

becomes:

Then, we need to recognize how to rewrite fractional exponents. In a fractional exponent, the numerator stays as the power to which we are raising our base. The denominator becomes the index of our root. Thus, our fractional exponent becomes:

Four was the denominator of our fractional exponent, so it became the index of our root. In other words, something raised to the power of  is the same thing as taking the fourth root of that something.

Example Question #31 : Powers & Roots Of Numbers

How can  be rewritten ?

Possible Answers:

Correct answer:

Explanation:

To solve this problem, we must remember exponent rules. The powers here need to be added, since the powers are both raising to the same number. The final answer is  or .

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